Reversible ionic bond mechanism in self-healing of natural rubber: A review

Self-healing materials have garnered significant attention for their potential to heal damage when it occurs. Elastomers, particularly natural rubber, have been a focal point of extensive research in the realm of self-healing materials. The ability of self-healing in natural rubber not only promises to extend the service life of rubber-based products but also offers new avenues for recyclability and reprocessability, contributing to environmental protection efforts. A key challenge in the self-healing of natural rubber has been to enhance its self-healing capabilities without compromising its mechanical properties. As a result, various self-healing mechanisms such as hydrogen bond, Diels–Alder (D-A) reaction, disulfide bond, imine bond, and ionic bond have been thoroughly investigated. Among these mechanisms, reversible ionic bonds or ionic interactions have emerged as particularly influential in facilitating the self-healing of natural rubber. This mechanism is easily incorporated into the structure of natural rubber due to its high stability, enabling natural rubber to exhibit promising self-healing properties. This review delves into a comprehensive statistical analysis of numerous published articles and focuses on the exploration of the ionic bonding mechanism in the context of self-healing in natural rubber. Additionally, it provides a succinct introduction to specialized tests designed to assess the self-healing in natural rubber focusing on related methods for ionic bonds mechanism evaluation, namely swelling test and healing efficiency test.